I was looking at a few old threads for the same topic and they just seemed to list batteries with mixed confirmations on whether or not they work with the touchpad. I have an external battery at the moment that though charges the TP it says the error message of may not charge properly.

So what amp/voltage does the touchpad require to charge properly and are there any external battery packs that do that? Ideally I was looking for something between 7000mah and 13000 so not something that is too big to carry around.

In order to charge the TouchPad at "FULL" rate, the external Battery needs to emulate the Data Pin configuration of the TouchPad Barrel Charger.

This requires the Data Pins to be bridged and a 240K Resistor to +5V and 300K Resistor to Ground. Without this, the TouchPad will only trickle charge from a 5V source, irrespective of the Current capability of the source.